Regional rainstorm changes in China: Ensemble projection via RegCM4 dynamical downscaling

doi:10.13745/j.esf.sf.2021.9.61

Abstract

Abstract:

Regional rainstorms usually occur over large areas and persist for a long time, which can lead to severe flooding disasters and pose serious risks to the sustainable socioeconomic development of the affected areas. Thus, projection of regional rainstorm changes is crucial for climate change adaptation and disaster risk management in China. Based on regional dynamical downscaling with RegCM4 from four global climate models, this study firstly identifies regional rainstorm events by a “tracing” method, and then projects changes in 5 rainstorm parameters—frequency, duration, average amount, average affected area, and comprehensive intensity—during the 21^st century under the RCP4.5 scenario. The resulting ensemble projection indicates national-scale rising trends in all 5 rainstorm parameters toward the end of the 21^st century. Relative to 1986-2005, the proportion of regional rainstorms with high rainstorm parameter values is projected to increase during mid- and end-21^st century, while small rainstorm parameter values occur less frequently. Spatially, the frequency, duration, and amount of regional rainstorms are projected to increase across eastern China, with similar spatial distribution patterns for the amplitude increase. The largest increase is in the middle and lower reaches of the Yangtze River valley and southern China, with larger increases towards the end of the 21^st century.

Key words: regional rainstorm events, regional climate model, dynamical downscaling, ensemble projection

CLC Number:

P467

ZHOU Botao, CAI Yiheng, HAN Zhenyu. Regional rainstorm changes in China: Ensemble projection via RegCM4 dynamical downscaling[J]. Earth Science Frontiers, 2022, 29(5): 410-419.

Figures/Tables 7

Fig.1 Temporal evolution of (a) frequency, (b) duration, (c) average precipitation amount, (d) average influential area, and (e) comprehensive intensity of regional rainstorm events averaged over China (time series is smoothed with 20-year running mean) simulated by MME and its ensemble members

Table 1 MME and individual model projected trends of the percentage anomalies (relative to 1986-2005) of the metrics for the regional rainstorm events averaged over China during 2006-2099 (%)

指标	各模式下的指标值
指标	CdR	EdR	HdR	MdR	MME
频次	1.59	1.73	0.75	0.86	1.23
持续时间/d	1.18	0.36^*	1.44	0.18^*	0.81
平均降水量/mm	0.67	0.45	0.59	0.51	0.56
反映平均影响范围的网格点数	1.34	0.65	0.97	1.48	1.14
综合强度/10²	2.15	1.04	1.85	1.42	1.65

Table 2 MME simulated values of the regional rainstorm events over China for different periods

指标	各时期的指标值
指标	1986—2005	2046—2005	2080—2099
总频次	37.1	41.7	39.5
持续时间/d	2.2	2.3	2.4
平均降水量/mm	68.8	72.0	72.5
反映平均影响范围的网格点数	79.0	85.0	88.0
综合强度/10²	8.7	9.7	10.1

Fig.2 MME simulated distribution of the percentage (%) of (a) duration, (b) average precipitation amount, (c) average influential area, and (d) comprehensive intensity of regional rainstorm events at different scales to the total events over China. The abscissa in (b), (c), and (d) indicates the mean value of the range.

Fig.3 MME simulated (a) frequencies of different categories of regional rainstorm events and (b) their ratio (%) to the total events over China

Fig.4 MME projected changes (relative to 1986-2005) of (a1, a2) frequency, (b1, b2) duration (days), and (c1, c2) accumulative precipitation amount (mm) of regional rainstorm events during the middle (left-hand panels) and the end (right-hand panels) of the 21st century

Fig.5 Spatial distribution of the SNR for (a1, a2) frequency, (b1, b2) duration (days), and (c1, c2) accumulative precipitation amount (mm) of regional rainstorm events during the middle (left-hand panels) and the end (right-hand panels) of the 21st century (the number in the lower left corner indicates the proportion of areas where the SNR is larger than 1)

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